Solid tires are often used in severe services where exposure to sharp objects would puncture pneumatic tires. These services include ground support vehicles at airports, forklifts, pay-loaders, scrap metal yard vehicles, and skid steel loaders.
Solid tires are often press-fit onto rims such that there is no slippage between the rims and tires during service when a substantial torque is applied to the tires. High torque is applied to tires that are used as drive wheels and/or braking wheels. When a solid tire is initially manufactured, the shape and dimension of the bead area is carefully controlled such that the force required to press the tire on the rim is enough to grip the rim in service, but not so much that the rim or tire is damaged. Some tires have steel cables imbedded near the bead area to insure that the tire with retain its initial gripping force during service. Other tires are formed directly into steel bands and the steel bands are pressed onto the rims. These are referred to as “steel band press ons”. The ID of the bands must be within narrow limits due to the rigid properties of the both the steel bands and the rims. Other tires are formed of a blend of rubber and nylon fibers. The nylon fibers help the tire hold its shape and retain its gripping force during service. These tires are referred to as “friction based” solid tires.
It is desirable to retread solid tires after the tread surface has been worn. This saves money and reduces the environmental waste from otherwise discarded used tires. Retreading of solid tires generally comprises: buffing the tread surface of the used tire to expose fresh tread rubber surface; applying uncured replacement tread rubber to the tread surface; and curing the uncured tread rubber with heat and pressure to bind it to the tire body.
There are several challenges to economically and effectively retreading solid tires. These include:    “Spin-on-the-rim”: When a tire body is exposed to heat and pressure during the curing operation, the bead surface changes shape and hardness such that the retread tire is prone to slip when press-fit back on the rim. This problem is known as spin-on-the-rim. Overcoming this problem is a long felt need in the industry. U.S. Pat. No. 4,566,515, to Kühn entitled “Wheel and Solid Tire Assembly Having Locking Ring”, discloses an improved rim (“wheel” as used therein) suitable for preventing spin-on-the-rim of retread solid tires. It does not teach or suggest any means for retreading a solid tire. U.S. Pat. No. 5,667,812 to Shimizu entitled “Tire Vulcanizing Mold” discloses a mold suitable for forming a new solid tire. It does not teach or suggest any means for retreading a solid tire. U.S. Pat. No. 3,808,076 to Barwell entitled “Methods and Apparatus for Applying Tread to Tyres or Wheels” discloses a method for retreading solid tires. It does not, however, teach or suggest any means to minimize spin-on-the-rim.    Appearance and dimensional accuracy: Solid tires often suffer deep gouges in their sidewalls due to exposure to sharp objects in service, such as when the tires are used on forklifts in scrap metal yards. The gouges are often filled by hand with uncured rubber that is then cured. This causes problems in obtaining a dimensionally accurate and cosmetically acceptable final product due to variability in the amount of rubber applied. The article “Niche Marketing to Improve Margins” by Marvin Bozarth and published in the September 1999 issue of the ITRA Journal describes the need for dimensional accuracy and cosmetic acceptability in retread solid tires. This article is incorporated herein by reference.    Width variance of tires: Solid tires that are nominally the same size (e.g. 7.00-12) often are produced with a variety of widths. This variability had heretofore made it impractical to use a single C mold to retread solid tires from various manufacturers and with various sidewall designs.
There is a need, therefore, for an improved process for retreading solid tires that is suitable for solid tires that are of various widths and can produce a product that has minimal spin-on-the-rim, is dimensionally accurate and is cosmetically acceptable. There is also the need for a mold for curing retread solid tires that is adaptable to tires that are nominally the same size but in actuality have various widths. There is also the need for an improved retread tire wherein said improved retread tire is suitable for brake wheel and/or drive wheel service.